Previously, to generate microscopic bubbles in liquid filled up in a container, a foaming nozzle which spouts a high-pressure gas (air) higher than an atmospheric pressure from the upside into the liquid is generally known. As this kind of the foaming nozzle, a milk-steaming nozzle provided at an espresso making machine is disclosed in Patent Document 1 (Japanese Patent Application Laid-open No. 2004-073442 A).
In general, the espresso making machine forcibly extracts by packing coffee beans deeply roasted and minutely grinded into a cup-type metallic filter, putting the pressure (which is usually about nine atmospheres) higher than one atmosphere (atmospheric pressure), and pressurizing the coffee beans of about one ounce (30 mL) with hot water of about 90-100° C. at the extraction time of 20-30 seconds. Moreover, such the espresso making machine is arranged a steaming-nozzle to blow a high-pressure and high-temperature steam generated in a tank at the behind (or right and left) of on-off valve of the coffee extraction portion. When heating or warming the milk to put in the coffee such as the espresso etc. and the beverages (drinks), the high-temperature steam is spouted from the steaming-nozzle to these liquids, and the above milk and beverages, etc. are heated without using the fire.
FIG. 1 shows a lateral view of a general foaming nozzle 100. In FIG. 1, the foaming nozzle (steaming-nozzle) 100 is connected to a high-pressure gas (steam) generating device (not shown) at the side of the base end (the upside of FIG. 1), and a high-pressure and high-temperature steam generated by the high-pressure gas (steam) generating device is sent to a tip portion through a flow passageway 101 formed in the foaming nozzle 100. Moreover, a chip body 102 is mounted on the tip of the foaming nozzle 100 by a screw connection and so on.
FIG. 2 shows a bottom view of the chip body 102 of the general foaming nozzle 100. As shown in FIG. 2, a plurality of (in this example, four) spouting holes 103 having the same diameters are provided on the concentric circle at equal intervals on the bottom of the chip body 102. Due to the structure of the chip body 102 equipping a plurality of the spouting holes 103, the steam which is sent from the high-pressure gas (steam) generating device through the flow passageway 101 is in radial spouted from the tip portion of the nozzle 100 downward. The liquid (milk etc.) in the container, arranged in the tip portion of the foaming nozzle 100 downward, is heated by the steam spouted from the spouting holes 103.
The milk foamed by the above steaming-nozzle is, for example, used to cappuccino, café-latte etc. Nowadays, a foaming work (steaming), while heating or warming the milk using the steaming-nozzle, is done by the craftsman named “barista”, and the popularity of foam-art (so called as “latté-art” or “coffee-art”) putting the patterns based on heart and rosette, etc., while pouring the foamed milk produced by the work (steaming) on the surface of the coffee such as espresso, etc., is growing.